MX2010007470A - A fault current limiter. - Google Patents

Abstract

A fault current limiter (FCL) includes a series of high permeability posts (1) for collectively define a core for the FCL. A DC coil (2), for the purposes of saturating a portion of the high permeability posts (1), surrounds the complete structure outside of an enclosure in the form of a vessel (3). The vessel (3) contains a dielectric insulation medium (4). AC coils (5), for transporting AC current, are wound on insulating formers (6) and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil (5) in the corresponding high permeability core are opposing. There are insulation barriers (7) between phases to improve dielectric withstand properties of the dielectric medium.

Description

A LOSS CURRENT LIMITER Field of the Invention The present invention relates to a leakage current limiter. The invention has been developed primarily for a high voltage saturated core loss current limiter and will be described with reference to that application. However, the invention is not limited to that particular field of use and is also suitable for low voltage, medium voltage, extra high voltage and ultra high voltage loss current limiters. BACKGROUND OF THE INVENTION Saturated core loss current limiters (FCLs) are known. Examples of superconducting loss current limiting devices include: The U.S. Patent. 7193825 by Darmann et al. The U.S. Patent 6809910 to Yuan et al. The U.S. Patent 7193825 from Boenig. The Patent Application Publication of E.U. Number 2002/0018327 of Walker et al. The leakage current limiters described are for use with dry-type copper coil devices and, in practical terms, are suitable only for saturated DCLs with direct current that use air as the main isolation medium. Is The main means of static isolation between the AC phase coils in a polyphase FCL and between the AC coils and the steel core, the CD coil, the cryostat and the main structure is provided by a suitable distance in the air. This substantially limits the FCL to "dry type" insulation technologies. Dry type technologies, usually refers to those techniques of construction of transformers that use electrically insulated copper coils, but only normal static air and isolated solid insulation barrier materials as the balance of the insulation medium. In general, air forms most of the electrical insulation material between the high voltage side and the ground components of the FCL. These ground components include the steel structure and the box. The use of dry type insulation limits the FCL to lower voltage ranges of AC line voltages up to approximately 39 kV. Transformers and dry type reactors are commercially available only up to voltage levels of approximately 39 kV. As a result, the technology currently demonstrated for CD saturated FCLs is not suitable for extension in high voltage versions. Dry type designs result in an inability to design a practically dimensioned compact structure that uses air as insulation medium when handling higher voltages. One of the main emerging markets for FCLs is the medium to high voltage range (33 kV to 166 kV) and extra high voltage (166 kV to 750 kV). When operating within these voltage ranges, the technique and descriptions in the currently described literature of saturated FCLs CD are not practical. The main reason is due to the static voltage design considerations, for example, the failure of the air insulation medium between the high voltage copper coils and the cryostat or steel core or CD coil. Frequently it is necessary that the high voltage phase coils, at medium to high voltages (greater than 39 kV), be immersed in one of: ß an insulating gas (such as SF6, nitrogen or the like). ß a vacuum (more than 10 ~ 3 mbar). ß a liquid such as a synthetic silicone oil, vegetable oil or other commonly available insulating oils used in the technology of transformers and reactors of medium voltage, high voltage and extra high voltage. When a high-voltage device is immersed in such an insulating medium, that medium is frequently referred to as the "volumetric isolation medium" or the "dielectric". Typically, the dielectric will have a capacitance relative of the order of approximately 2 to 4, except for the vacuum that has a relative capacitance equal to 1. This so-called dielectric insulation means has properties of resistance to electrostatic failure that are much higher than those of atmospheric air if judiciously used to limit the maximum distance between solid insulation barriers and optimizing the dielectric distance filled with respect to the failure properties of the particular liquid or gaseous dielectric. The commonly available volumetric insulating gases and liquids typically have a resistance to failure of the order of 10 to 20 kV / mm, but they are commonly used in such a way that the average charge of the electric field does not exceed approximately 6 to 10 kV / mm. This safety margin for the fault load value is required because, even if the average charge of the electrostatic field is 6 to 10 kV / mm, the peak charge of the electrostatic field along any isostatic line of the electric field It can be 2 to 3 times the average due to various effects of intensification of the electrostatic field. In general, there are five main desirable requirements of a liquid or dielectric gas for high voltage volumetric insulation requirements in hosted plants such as transformers and reactors and in leakage current limiters: • The dielectric must show a very high specific resistance. • The dielectric losses must be very low. • The liquid must be able to accommodate solid insulators without degrading that solid insulation (for example, isolation from spiral to winding in windings or epoxy). • The resistance to electrical failure must be high.

• The medium must be able to remove thermal energy losses. Solid isolation techniques at medium to high voltages (ie, at operating voltages greater than 39 kV) are not commonly available for housed devices such as transformers, reactors and leakage current limiters. The disadvantage of solid insulation techniques is the presence of unavoidable voids within the volume of solid insulation or between surfaces of dissimilar materials such as between coil insulation and other solid insulation materials. It is well known that voids in solid insulation with high voltages produce a high electrical charge within the vacuum due to the effect of field intensification. This causes the physical failure of the surrounding material due to partial discharges and, eventually, can lead to drag and failure. complete of the device. It will be recognized that the CD saturated saturation current limiter employing single or multiple CD coils to saturate the steel core, such as those described in the aforementioned prior art, has fundamental problems when the copper AC phase coils already they can not be of a "dry type" construction or when the main means of isolation of the entire device is air. A significant problem in such devices is the presence of the steel cryostat to cool the HTS CD coil and the HTS CD coil itself. The cryostat and the coil and the steel cores are essentially at a ground voltage with respect to the AC phase coils. As a collateral problem, but one that improves insulation requirements for all high-voltage plants and equipment, the basic insulation design must also meet certain electrical engineering standards that test tolerance to various types of surges and impulses. turned on for predetermined periods of time. An example, in Australia, of such standards is the following: ° AS2374 Part 3. Insulation and dielectric level tests including energy frequency (PF) and ignition pulse tests (LI) of the complete transformer. • AS2374 Part 3.1. Testing of insulation levels and dielectrics - External voids in the air. • AS2374 Part 5. Capacity to withstand short circuits. These standards do not form an exhaustive list of standards that high-voltage electrical equipment must meet. It is recognized that each country has its own standards that cover these same areas of design and the reference to the standard of an individual country does not necessarily exclude any standard from another country. Ideally, a device is built to meet multi-country standards. Adherence to these standards results in a BIL (basic insulation level) for the device or a "DIL" (insulation design level), which is commonly a multiple of the basic voltage of the AC line. For example, a 66 kV medium voltage transformer or other hosted device such as an FCL may have a BIL of 220 kV. The requirement to comply with this standard results in a static voltage design that is more difficult to accomplish, practically than only from a consideration of the AC line voltage. The applicable standards and this requirement have resulted from the fact that an installation Experimental electrical practice is temporary overvoltage that can be experienced by plants and devices within a complex network, for example, electrical discharge overload and disconnection overvoltages. Hence,, all the equipment in an electrical network has a BIL or DIL appropriate for the transitory voltages expected in the worst case. An initial consideration of the static design problem for CD saturated high-voltage loss current limiters can result in the conclusion that the problem is easily solved only by housing the high-voltage AC copper coils in a suitable gas or electrical insulating liquid. . However, the problem with this technique is that the steel core must pass through the container that contains the gas or liquid. Mechanically, it is difficult to solve the design of this interface for a long-term service. However, more importantly, electrostatically the solution to the problem of the interface is much more complex and any solution can be prone to failures or prove to be non-economic. The problem is that a seal must develop between the container containing the dielectric fluid and the high permeability core or, alternatively, a method for isolating the HTS cryostat from the fluid. Another possibility is the use of high barriers Dry solid voltage between the phases and between the phases and the steel core and the cryostat or a high voltage insulation layer around the copper phase coils and in intimate contact with the phase coils. However, this has a significant harmful side effect. It is known that the static electric field in a combination of air and other materials with higher relative capacitance, always results in an intensified electric field in the material or fluid with less capacitance (ie, air). For example, consider a conductive copper cylinder with a normal insulation layer to represent the turn-to-turn insulation, according to equation 1.

Equation 1 where Um = AC phase voltage with respect to ground R = radius of a copper cylinder that includes external insulation [mm] r = radius of an uninsulated copper cylinder [mm] d = distance from the center of the cylinder to the nearest ground plane [mm] E2 = relative dielectric constant of the insulation covering the cylinder • Ei = relative dielectric constant of the volumetric insulation in which the cylinder is submerged (which is equal to 1 for the air) • x = distance from the center of the cylinder to a point outside the cylinder [mm] • Ex = gradient of the electrostatic field at the point x [kV / mm] The effect of field intensification is represented by the factor E2 / E1 and is of the order of 2 to 4 for common everyday materials, except in the case of using a vacuum, which has a relative capacitance equal to 1. By providing additional solid or other insulation material (higher electrical capacitance than air), the electrostatic charge on the FCL volumetric air insulation is increased. The better the quality of the high-voltage insulation, the higher the effect of field intensification. Therefore, the barriers of solid dielectric insulation in an FCL, otherwise isolated by air, is not a technically desirable option for high voltage FCLs over 39 kV and, really, it is not expected that this technique is used for produce high voltage transformers of dry type to more than 39 kV, for example. In fact, highly adequate techniques have not yet been discovered and this is the reason why high-voltage transformers above 39 kV they are isolated with a liquid or dielectric gas. What has been discussed above is the reason why the frequently housed high-voltage electrical equipment is completely immersed in electrically insulating dielectric fluid or gas. That is to say, the insulated copper coils and the steel core of transformers and reactors are housed inside a container that is then completely filled with a dielectric medium that is a fluid. This substantially reduces the electrostatic voltage design problems detailed in the above discussed. The insulating medium (eg oil, vacuum or SF6) fills all voids and volumetric distances between the high-voltage components and the components that are essentially at a neutral or earth voltage. In this case, solid insulation barriers can be incorporated in the volumetric insulating dielectric and, for many liquids such as oil, the division of large distances with solid insulation improves the quality of the total electrostatic insulation by increasing the resistance of the dielectric fluid fault field. This is due to the fact that the relative capacitance of the oil and the solid insulation are very close to each other (so that the effects of field intensification decrease in comparison with the air) and the failure voltage of the volumetric dielectric medium (expressed in kV / mm) improvement for smaller distances between the insulation barriers. A major problem with the total immersion technique is that it is not easily adaptable to saturated FCL designs CD or other devices that incorporate a superconducting coil as the CD saturation element. This is because the superconducting coil and its cryostat or vacuum vessel are a component of the FCL that, necessarily, it must also be submerged in the dielectric fluid. The established incorporated literature clearly points to four main criteria for an FCL that can be commercialized, that is possible and that can be manufactured: • It must have a low insertion impedance so that it is invisible to the network when there are no losses and when it provides a flow of peak energy. • It must not produce more than 0.5% of the THD that merits harmonics (total harmonic distortion) or that the end user requires. • It must provide an adequate cut of the loss current, between 20 and 80%. • The design must be able to be increased at high AC voltages (greater than 6 kV) and at high alternating current (greater than 0.6 kA). Classic designs of the saturable core FCL detailed in the prior art suffer from the major disadvantages of not being suitable for high voltage and high alternating current designs. Both disadvantages arise from the lack of a refrigerant (other than air) and / or a liquid or gaseous dielectric. Even if a liquid or gaseous dielectric is used in the classic saturable FCL design, a significant increase is still required to allow access to the cryocooler, the cryostat and the cryostat accessories. In addition, special seals have to be produced and tested to isolate the cryostat's supply lines (electrical power, electrical signals) from the dielectric. In designs of high alternating current, the copper area in cross section required to conduct the required electrical current is much greater when considering only an air-cooled design. It is not unusual for this cross-sectional area to be up to five times larger, this can make the dimensions of the CA coil too large to accommodate the minimum dimension of the yoke of the core frame, requiring a larger yoke to maintain space electrostatic. This increases the tread and mass of the classic air cooled / saturable FCL isolated by air. Everything discussed in the prior art throughout the specification should not be considered in any way as an admission that such prior art is widely known or that it forms part of the general knowledge common in the field. SUMMARY OF THE INVENTION An objective of the preferred embodiments of this invention is to improve one or more of the aforementioned disadvantages or to provide a useful alternative. Another object of the preferred embodiments of the invention is to overcome one or more of the aforementioned disadvantages by inverting the conventional relative locations of the AC and DC coils with an FCL. These modalities allow the entire structure to be immersed in a dielectric. According to a first aspect of the invention, there is provided a high voltage loss current limiter including a magnetically saturable core and at least one AC phase coil wound around a portion of said saturable core, wherein said core is magnetically saturable and said at least one AC phase coil are housed within a housing and a polarization coil is disposed outside and around said housing which, during the conditions of operation without loss of said current limiter, polarizes said core in magnetic saturation for an insertion impedance without loss in low steady state, but during the loss conditions, it extracts said core from the magnetic saturation to thereby provide a limiting impedance of increased current in said electrical circuit. In one embodiment, the high permeability core is selected from one or more of a steel rolling material; a sweet steel; or other forms of magnetic steel, ferrite materials or a ferromagnetic material for transformer. In one embodiment, the core is in the form of a rectangular array of core post with CA phase coils wound, each on the respective core poles and electrically interconnected in such a way that the magnetic field senses produced by the AC coils are opposite. In one embodiment, the leakage current limiter includes a container surrounding the coils CA to contain a dielectric insulation means and a cooling medium for said AC coils. In one embodiment, the CD coil is a superconductor and, more preferably, a high temperature superconductor housed in a cryostat and cooled by a cryocooler.

In one embodiment, the CD polarization coil coincides with a coaxial with the AC phase coils, such that said portion of the saturable core is completely saturated. In a modality, the magnetically saturable core and the AC coils are immersed in a dielectric that is in the form of a solid, liquid or gas and that includes air in any atmosphere including vacuum. In one embodiment, the core posts are rectangular in cross section and of constant cross section along the extensions thereof. In one embodiment, the magnetically saturable core is constructed of a steel rolling material; a sweet steel; or other forms of magnetic steel, ferrite materials or a ferromagnetic material for transformer. In one embodiment, the poles of the core are inclined toward the ends thereof, whereby, during operation without loss of the current limiter, substantially all said core is saturated. According to a second aspect of the invention, a leakage current limiter is provided which includes: an input terminal for electrically connecting to a power source that provides a charging current; an output terminal for electrically connecting with a charging circuit that carries the charge current; a magnetically saturable core; an AC coil wound around a longitudinal portion of the core to convey the load current between the input terminal and the output terminal; and at least one CD coil for inducing a magnetic field in at least a portion of the core and extending around an intermediate longitudinal zone receiving the core and coil CA, wherein the field magnetically polarizes the core in such a way that the AC coil moves from a low impedance state to a high impedance state in response to one or more characteristics of the load current. In one embodiment, in the low impedance state, the portion is magnetically saturated. In one embodiment, in the low impedance state, the core is magnetically saturated longitudinally beyond the portion. In one embodiment, in the high impedance state, the portion is out of magnetic saturation. In one embodiment, in the low impedance state, the impedance of the AC coil is substantially equal to the theoretical impedance of the air core of the AC coil. In one embodiment, one of the one or more features is an increase in charge current beyond a predetermined current value. In one embodiment: the core includes a plurality of posts; the longitudinal portion is segmented between the posts; and the CA coil includes a plurality of coil segments that are wound around the respective poles. In one modality, the posts are parallel. In one embodiment, the posts extend longitudinally. In one embodiment, each post has a substantially uniform cross section. In one embodiment, the posts have substantially equal cross sections. In one embodiment, the cross section of the posts has at least one axis of symmetry. In one embodiment, the cross sections of the posts are symmetrical. In one embodiment, the posts co-extend substantially within the intermediate zone. In one modality, the posts are separated one from the other. In one embodiment, the posts extend longitudinally beyond the CD coils. In one embodiment, the coil segments co-extend substantially longitudinally in the intermediate zone. In one embodiment, the AC coil extends longitudinally beyond the CD coils. In one embodiment, each post extends longitudinally beyond the respective CA coil. In one embodiment, the load current includes three phases and the loss current limiter includes three pairs of input terminals and output terminals for the respective phases. In one embodiment, the loss current limiter includes six poles arranged in three pairs, wherein each pair of poles is associated with a respective pair of input and output terminals for transporting the corresponding phase of the load current. In one modality, the posts, in each pair of posts, are fixed to each other. In one embodiment, each post includes longitudinal ends and at least one end of each post is fixed to an adjacent end of the other post in the same pair.

In one embodiment, both ends of each of the posts are fixed to the respective adjacent ends of the other post in the same pair. In one embodiment, the posts are fixed magnetically and physically by a material of high permeability. In one embodiment, the posts, in each pair, are adjacent to each other and include separate opposed surfaces. In one embodiment, the opposing surfaces are substantially planar. In one embodiment, the opposing surfaces are substantially parallel. In one embodiment, the opposing surfaces are substantially co-extensive. In one embodiment, the loss current limiter includes a housing for defining the intermediate zone. In one embodiment, the housing contains a dielectric material. In one embodiment, the AC coil is received within the dielectric. In one embodiment, the CD coils include a high conductivity material. In one embodiment, the high conductivity material is selected from: copper; aluminum; a high temperature superconductive material; a low temperature superconductive material. According to a third aspect of the invention there is provided a method for limiting the current including the steps of: providing an input terminal for electrically connecting to a power source that provides a charging current; providing an output terminal for electrically connecting to a charging circuit that carries the charging current; provide a magnetically saturable core; winding an AC coil around a longitudinal portion of the core to transport the charge current between the input terminal and the output terminal; and inducing a magnetic field in at least one portion of the core with at least one CD coil, wherein the CD coil extends around a longitudinal intermediate zone that receives the core and the AC coil and, where the field magnetically polarizes the core such that the AC coil moves from a state of low impedance to a state of high impedance in response to one or more characteristics of the load current. According to a fourth aspect of the invention, a loss current limiter is provided which includes: an input terminal for electrically connecting to a power source that provides a charging current; an output terminal for electrically connecting with a charging circuit that carries the charge current; a magnetically saturable core; an AC coil wound around a longitudinal portion of the core, for transporting the charge current between the input terminal and the output terminal; and at least one CD coil that is in an open core arrangement with the AC coil to induce a magnetic field in at least a portion of the core, the CD coil extending around an intermediate longitudinal zone that receives the core and the AC coil , wherein the field magnetically polarizes the core such that the AC coil moves from a low impedance state to a high impedance state in response to one or more characteristics of the load current. According to a fifth aspect of the invention there is provided a method for limiting the current using a leakage current limiter, including the method: electrically connecting a power source to a input terminal to provide a charging current; electrically connecting a load circuit to an output terminal to draw the load current; provide a magnetically saturable core; providing an AC coil wound around a longitudinal portion of the core to convey the load current between the input terminal and the output terminal; and providing at least one CD coil that is in an open core arrangement with the AC coil to induce a magnetic field in at least a portion of the core, the CD coil extending around an intermediate longitudinal zone that receives the core and the coil CA, wherein the field magnetically polarises the core such that the AC coil moves from a low impedance state to a high impedance state in response to one or more characteristics of the load current. According to a sixth aspect of the invention, a leakage current limiter is provided which includes: three input terminals for electrically connecting the respective phases of a three-phase power source which provides a three-phase charging current; three output terminals that are electrically connected to the respective phases of a charging circuit that carries the charge current; a magnetically saturable core having three pairs of posts, each post having a longitudinal portion; three CA coils wound around the portions of the respective pairs of poles to transport the load current between the input terminals and the output terminals; and at least one CD coil for inducing a magnetic field at least in the portions and extending around a longitudinal intermediate zone that receives the poles and AC coils, wherein the field magnetically polarizes the core in such a way that the AC coil it moves from a state of low impedance to a state of high impedance in response to one or more characteristics of the load current. In one embodiment, each CA coil includes two coil segments that are wound each around the respective portions of the poles in the pair of poles. According to a seventh aspect of the invention there is provided a method for limiting the current using a leakage current limiter, the method including the steps of: electrically connecting to the respective phases of a three-phase power source, three input terminals to provide a three-phase load current; electrically connect to the respective phases of a charging circuit, three output terminals to draw the charging current; providing a magnetically saturable core having three pairs of posts, each post having a longitudinal portion; providing three CA coils wound around the portions of the respective pairs of poles to transport the charge current between the input terminals and the output terminals; and providing at least one CD coil for inducing a magnetic field at least in the portions and extending around a longitudinal intermediate zone that receives the poles and coils CA, wherein the field magnetically polarizes the core in such a way that the coil CA moves from a state of low impedance to a state of high impedance in response to one or more characteristics of the load current. According to an eighth aspect of the invention, a core for a leakage current limiter is provided, the core including at least one longitudinally extending pole having at least two portions that are magnetically saturable and which, in one, are receive inside the respective coil segments of a coil CA which, in turn, is received inside a CD coil. In one embodiment, the portions are separated. In one embodiment, the core includes two similar parallel posts that have respective portions. In one modality, the posts are fixed. In one embodiment, the posts are fixed to each other. In one embodiment, each post extends between a first end and a second end, wherein the first end and the second end of one of the posts are adjacent to the first end and the second, respectively, of the other post. In one embodiment, the core includes a yoke to extend between the first ends to secure the posts to each other. In one embodiment, the core includes an additional yoke to extend between the second ends to secure the posts to each other. In one embodiment, the posts include post laminations. In one embodiment, the yoke includes laminations. In one embodiment, the post laminations and the yoke laminations are interlaced. In one modality, the core includes six poles that they extend longitudinally arranged in three pairs. According to a ninth aspect of the invention, a leakage current limiter is provided which includes a core of the eighth aspect of the invention. According to a tenth aspect of the invention, there is provided an electrical distribution system that includes at least one leakage current limiter of one of the first, second, fourth, sixth and ninth aspects of the invention. The reference throughout this specification to "one modality", "some modalities" or "one modality" means that a particular feature, structure or characteristic described in connection with the modality is included in at least one embodiment of the invention. present invention. Therefore, the appearance of the phrases "in a modality", "in some modalities" or "in a modality", in some parts throughout this specification, do not necessarily refer to the same modality, but it is possible . In addition, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to that of ordinary experience in the art from this description, in one or more embodiments. As used herein, unless otherwise specified, the use of ordinal adjectives - - "first", "second", "third", etc., to describe a common object, merely indicates the reference to different examples of similar objects and does not intend to imply that the objects so described must be found, in a given sequence, in order either temporarily, spatially, or in some other way. BRIEF DESCRIPTION OF THE DRAWINGS The presently preferred embodiments of the invention will now be described with reference to the following annexed drawings in which: Figure 1 is a schematic view of a core structure of experimental FCL; Figure 2 illustrates the results of an FEA analysis in the structure of Figure 1; Figure 3 illustrates a closed core structure for an FCL with the coil CA and the coil CD superposed and coaxial, ie the two coils are wound around the same column of the closed core; Figure 4 illustrates an experimental closed core structure with associated search coils to allow investigation of the nature of the insertion impedance; Figure 5 is an illustration of the results of the experiment conducted with the structure of Figure 4; Figure 6 summarizes the measured results of the insertion impedance for the previous experimental structures; Figure 7 is a schematic cross-sectional view of a three-phase open core loss current limiter according to said invention; Figure 8 is a schematic view of the electrical interconnection of the windings in two of the core posts shown in the leakage current limiter of Figure 7; Figure 9 shows the results of the FEA analysis of the magnetic field and the relative permeability through the length of a core in the Z direction of Figure 7; Figure 10 shows a diagram of the magnetic field along a center line to the cores and crossing three pole cores in the X direction of Figure 7; Figure 11 shows a diagram of the magnetic field in the center of a single core post of Figure 7 with DC energization; Figure 12 shows a diagram of the DC magnetization of the core of Figure 7 with minor excursions CD around two otherwise saturated operating points; Figure 13 shows a diagram of the relative permeability in the middle of a core post of Figure 7 with respect to the energization of the CD coil and with 1,000 amperes of current in the 50-turn CA coil; Figure 14 shows a diagram of the DC magnetization of the core of Figure 7 as a function of the ampere turns of the DC with the total alternating current in the AC coil, such that the fluxes produced by each are opposite; Figure 15 is an alternative of the invention showing the same wound interconnection and that the lower yoke between two cores is retained; Figure 16 shows an arrangement of a three-phase open-core FCL design with three rows and two columns of steel cores and with electrical interconnections in each phase according to the detail in Figure 8; Figure 17 shows an alternative arrangement of the three-phase open-core FCL design with two rows and three columns of steel cores with electrical interconnections in each phase as detailed in Figure 8; Figure 18 shows a fixed alternative of the three-phase open-core FCL and with electrical interconnections in each phase according to the detailed in Figure 8; Figure 19 shows the experimental layout - - used for the measurements of density 'of flow and of impedance of insertion without loss in steady state CA and the characterization of the loss current and with electrical interconnections in each phase according to the detailed in Figure 8; Figure 20 shows the lossless insertion impedance characteristics measured for the experimental arrangement of the open-core FCL; Figure 21 shows the steady-state insertion impedance characteristics without loss at different AC voltages and currents; Figure 22 shows diagrams of the loss current characterization for an open-core FCL as a function of DC polarization; Figure 23 shows diagrams of the transient characterization of the flux density of the experimental open core arrangement; Figure 24 shows a diagram of the transient voltage of the DC circuit when the core is saturated to a degree beyond the region of influence of the AC coil and where the presence of the loss is detected as a slight drop in voltage between the coils. points of the arrows starting from t = 0.08 seconds; Figure 25 shows transient loss current diagrams of the experimental setup with and without - - the open-circuit FCL in circuit; Figure 26 shows the transient current characteristics of the DC circuit of the experimental setup of the open-core FCL; Figure 27 shows the experimental arrangement of the AC and DC coils for the measurement and characterization of the flux density, the insertion impedance without AC loss and the limiting capacity of the loss current of the fixed FCL with electrical interconnections in each phase according to the detailed in Figure 8; Figure 28 shows the steady-state insertion impedance with no measured loss of the experimental setup of the open-core fixed FCL compared to the measurement in the non-fixed open-core FCL with columns of the same dimensions; Figure 29 shows the comparison of the lossless insertion impedance measured between the fixed and non-fixed open-core arrangements and compared to several closed-core arrangements; Figure 30 shows the steady-state insertion impedance with no measured loss of the experimental setup of the open-core fixed FCL compared to the measurement in the non-fixed open-core FCL with columns of the same dimensions; Figure 31 shows characterization diagrams of the loss current for a fixed open-core FCL as a function of the polarization of the DC; Figure 32 shows a diagram of the flux density of the open-core FCL experimental setup, taken from a search coil around a steel column and located on the top of the CA coil of a fixed open-core FCL; Figure 33 shows the characteristics of the transient current of the DC circuit of the experimental setup of the fixed open-core FCL; Figure 34 is a schematic representation of an FCL in an electrical distribution system; Figure 35 is a schematic perspective view of a single-phase open core FCL in which the core includes two steel posts that are stacked end-to-end; Figure 36 is a top view of the FCL of the Figure 35; Figure 37 is a schematic perspective view of a single-phase open-core FCL in which the core includes a single energy-pressed post; - Figure 38 is a top view of the FCL of the Figure 37; Figure 39 is a schematic perspective view of a further embodiment of an FCL having a generally circular tread that includes yokes between the poles within the core; and Figure 40 is a schematic top view of the FCL of Figure 39; Figure 41 is a schematic perspective view of an FCL similar to that of Figure 39 without the yokes; Figure 42 is a top view of the FCL of the Figure 41; Figure 43 is a schematic perspective view of an FCL including a core having rectangular cross-section posts arranged in a stacked 3 x 2 arrangement; Figure 44 is a schematic perspective view of an FCL including a core having rectangular cross-section posts arranged in a 3 x 2 side-by-side arrangement; and Figure 45 is a schematic perspective view of an FCL including a core having rectangular cross-section posts arranged in a stacked 3 x 2 arrangement that are fixed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although a number of embodiments are described below, additional embodiments of the invention are described in Australian Patent Application No. 2009901138 filed on March 16, 2009, and of which priority is claimed. The detail of these modalities is expressly incorporated herein by way of cross reference. The following description, with reference to Figures 1 to 6, is intended to provide the recipient with a context about the embodiments of the invention. First, it is mentioned that the frequently used parametric fres of the preferred embodiments include: * Anúcieo: The cross-sectional area of the high permeability cores under the CA coil • Nac: The number of turns CA, • Ndc: The number of turns CD, • IdC: The DC coil current [amperes], • Iac: The AC coil current [amperes, rms], • F: The frequency of the electrical system, • Zb: The base impedance of the electrical system that is protisge • Z +: The impedance of the positive sequence of the system • IfP: The leakage current of the system • Ifr: The desired reduced loss current. The limitation of the leakage current and the Insertion impedances are functions of the above parameters. It will be known to those skilled in the art that the magnetization of a high permeability structure, as required in the field of FCLs, is prone to loss of flow due to the following two main effects: ° The marginal effect of the lines of the magnetic field around the CD polarization coil and return through a purely aerial trajectory. ° The return of the partial air / core flow where the flow enters the core but returns through an air path instead of a full path of high permeability. For example, an FEA analysis was conducted in the core structure shown in Figure 1. The relevant features of this core structure are: ° Width of the window dimension = 290 mm T Height of the window dimension = 350 mm @ Material: laminated steel core M6 T Laminations used to build the core: 0.35 mm core structure progressively coated ° Cross-sectional area of the core: 150 mm x 150 mm.

Other experimental details are shown in Figure 1 and the most complete results are shown in Figure 2. It was found that there was a loss of magnetic flux density in the columns and distant yokes. Table 1 below summarizes the results for the core structure of Figure 1 at the point of maximum flux density.

Table 1: Basic results of the flow density in the prototype core of Figure 1 The effect described herein is well known to those skilled in the art. The reduction in flux density on the CA core side from 2.12 Tesla to 1.95 Tesla, it may not seem, at first, a disadvantage. However, it is the measurement of the minor loop in the AC coil that reveals the problem. Although the minor loop of the CD side coil results in an average relative permeability of about 1.0, as expected for a saturated core, the smaller loop measured at the same current level of the CD coil reveals a relative permeability of 86. The result of a high insertion impedance for the device also reveals that the lateral CA core is not fully saturated despite observing the classic flattening of the BH curve. Procedures to reduce the loss of flow density and to conserve the CA side of the saturated core include: 0 Employing a higher cross-sectional area of the core along the entire structure. ° Non-uniform transverse cuts of steel. ° Reduce the total magnetic length of the steel between the AC and DC coils to produce a low profile core structure. However, as an alternative to these procedures, it is also practical to place the CA coils near the side columns as shown in Figure 3. Using this technique, the flow density in the columns immediately below the coils CA is substantially the same as that immediately under the CD coils. During steady-state operation, the flow of the AC coils must be such that the magnetic flux density in the portion of the steel core under influence is not derated or substantially changed, since this will lead to a higher insertion impedance than the minimum possible and would cause a harmonic content in the AC waveform without loss in steady state. During the limiting loss activity, the flow generated from the CA coils prevents that in the steel core by desaturating a portion of the steel core and causing the terminal impedance of the AC coil to rise. In this particular arrangement, it will also be recognized that yokes and external columns are no longer required, only central columns are needed. The problem associated with the loss of flux density in the column containing the CA coil is also associated with a higher impedance at steady state in the lossless state, also known as the insertion impedance. The insertion impedance associated with an AC coil is directly proportional to the gradient of the flux density against the graph of the magneto force - - motor (MMF). If the portion of the core under the influence of the AC coil is not fully saturated to a point where this inclination is minimized, then the insertion impedance will be high impractically. To illustrate the nature of the insertion impedance, an experimental arrangement was constructed in Figure 4 to measure it for various locations of the AC coil in a core with respect to the CD coil. A core and coil structure was constructed with the details shown in Table 2 and Table 3 below. Table 2 Table 3 Iron core factor 0.96 Iron integration magnet Walker Magnet employed Flushometer settings 25.5 x 0.96 x 100 = 2448 CD copper coils used (not superconducting) All aluminum construction and support - no mild steel was used. Scout bobbins directly coiled tightly in the core M6 laminated steel core (0.35 mm thick laminations) Now, reference is made to Figure 5. Confirmation of saturation on the CD side was made using search coils and Hall probes. The use of the Hall probes indicated the need to introduce a 1.3 mm air space in the core that was not used during the measurements of the insertion impedance. Other details of the experimental arrangement for the measurement of the insertion impedance include: o Current DC = CD of 100 amps or AC voltage = AC of 50 V or Frequency of voltage and AC current: 50 Hz or AC current = AC of 28 amps o Espiras CA = 50 0 AC coil resistance = 0.10 Ohms Figure 6 summarizes the results of the measured insert impedance. The minimum insertion impedance is achieved with the matching coil arrangement and with the minimum number of ampere turns in the CD coil required for saturation. All other arrangements, including those in which the CA coil is in the same column as the CD coil and in close proximity to the CD coil, result in a higher insertion impedance. The measurements of the insertion impedance as a function of the ampere turns have confirmed that the high permeability core under the influence of the AC coil, must not only be saturated but must be "super saturated" to have the theoretical minimum insertion impedance . As shown in Figure 34, the loss current limiter (FCL) is located in an electrical distribution substation. The FCL is mainly included to limit the loss current of a transformer, which is also illustrated. When a substation includes more than one transformer, it is possible to have a separate FCL for each of these transformers. However, in some modes, less than all transformers within a substation have an associated FCL. The FCL, on the downstream side, is it is electrically connected to an electrical distribution system of which the substation is part. In other modalities, the transformer and the FCL are located within a facility other than a substation. Indicative examples include an industrial location distribution network, between a co-generator and the rest of the network; and the protection of the main electricity grid from the contribution of the loss current of a wind farm, a wave generator, a hydro-generator or a solar farm. For the mode of Figure 34, the power station is a coal-fired power station. However, in other embodiments, the power station is one or more than one hydro station, one nuclear power station and one wind generator power station. With reference to Figure 7, a series of high permeability posts 1 is illustrated in a three-phase open core FCL arrangement according to one embodiment of the invention. The Z direction is defined to be along the longitudinal direction of the high permeability core, as shown. the posts are fabricated from transformer laminations and the rotational direction of the laminations is along the Z axis. It will be appreciated that the posts 1 collectively define a core for the FCL.

The high permeability posts 1 are made of a transformer steel rolling stock. In other embodiments, use is made of one or more of mild steel or other forms of ferrite materials of magnetic steel or of ferromagnetic material or of granular material such as a core made of consolidated ferromagnetic powder, or a glassy amorphous core. A CD 2 spool, for the purposes of saturating a portion of the high permeability posts 1, surrounds the entire structure outside the housing. The term "surround" or the like is used to describe how coil 2 circulates the housing or tank. That is, the CD coil extends around a longitudinal intermediate zone that receives the core and the CA coil. In the illustrated modalities, the core and coil or AC coils are disposed within a tank or other housing, and the CD coil circulates in the housing. This provides a number of packaging and performance advantages of the preferred embodiments. As will be mentioned later, the intermediate zones of the modalities are defined by the respective tanks. A container 3 contains a dielectric insulation means 4. This medium is also a cooling medium for the CA coils and may be ambient atmospheric air. There are CA 5 coils to transport the current alternating coils on insulation winding templates 6 and electrically interconnected with each other in such a way that the magnetic field senses produced by each coil CA n the corresponding high permeability core are opposite. There are insulation barriers 7 between the phases to improve the dielectric support properties of the dielectric medium. Preferably, the CD 2 coil is also a superconductor and, more specifically, it is a high temperature superconductor housed in a cryostat and cooled by a cryocooler (not shown). Figure 8 shows the electrical interconnection of two AC coils in the structure of Figure 7 showing the direction and direction of the windings relative to each other. By way of example, saturated open core FCL of the type shown in Figure 7 was analyzed using FEA. The continuous and alternating currents were staggered in order to find the optimal values of IdC and Iac for a given number of turns in each of these windings and to understand the nature of the magnetization of an open core. The parameters used were those for a substation FCL of the typical class of 15 kV and include: • Number of cores: 6 • Length of a core post: 0.6 m • Andean, the cross-sectional area of each core: 0.0225 m2, being 150 mm x 150 mm in Nac dimension: 50 Ndc: 500 • Idc: graduated from zero to 500 amps, (up to 250,000 turns of amperes CD on the CD coil) • Iac: graduated from zero to 1, 000 amperes rms. (up to 50,000 turns of AC amps in the AC coil) The material parameters used are those of the M6 transformer laminations and are 0.35 mm thick. Figure 9 shows the magnetic field distribution and the relative permeability across the length in the Z direction of the structure shown in Figure 7. The region of the. suitable core to place an AC coil, the saturated region of the high permeability core. This result shows, for example, that the CA coil should be designed in such a way that its height is 400 mm and that it is placed on the core at not less than 100 mm from either end of the core. Figure 10 shows a diagram of the magnetic field along a line passing through the - - center of three cores and in the X direction. This result shows that the magnetic field in all the cores is sufficient to saturate all six cores in an XY arrangement of the core poles despite the non-uniform distance from, and from the geometric relation with, the winding of the CD coil. Figure 11 shows the DC magnetization (Iac = 0) of the core in the central region of the core indicated in Figure 9. Figure 12 shows the lower curve of the CA magnetization excursion of the central portion of the core at two different values of the polarization current CD. From the consideration of Figure 11 alone one can draw the conclusion that an energization of the DC coil of 80,000 turns of ampere of the CD (equivalent to a CD of 160 amps in the CD coil of 500 turns) would be enough to saturate the nucleus However, consideration of the lower magnetization curves of the AC coil (Figure 12) and the relative permeability of the coil under the energization of the AC coil (Figure 13), shows that at least 140,000 turns of ampere coil are required. CD (that is, at least 280 CD amps in the CD coil) for the core to have a relatively low permeability and, consequently, give the AC coil a low insertion impedance.

Figure 12 shows that a current of up to 1,000 amperes in the AC coil would desaturate the core with a CD operating current as low as 160 A (80,000 amperes). This is undesirable and such a design will lead to a high insertion impedance, high THD, and a distorted current waveform. Compared, the lower calculation of the CD magnetization circuit is also shown at an operating point of 500 A, which is a more desirable point of operation. Under these conditions, the core is super-saturated under the CA coil and is a more suitable point of operation. In general, when considering the complete list of optimization variables, the combined calculations of CD magnetization and CD minor magnetization is not a direct procedure for finding suitable CD operation amps and requires a long FEA optimization process. To simplify the process, the inventor proposes a static magnetization analysis of the core with the AC coil energized up to the peak of the waveform of the current under maximum load. Figure 14 shows such a FEA calculation from which it is clear that, in this case, a DC magnetization of 150,000 ampere turns is required for the core to remain. in saturation in each and every one of the instantaneous points of the CA waveform. Practically, it is important that the limiter of - - loss current has a low insertion impedance. In the present embodiment, this is achieved by ensuring that the volume of the steel core, under direct magnetic influence by means of the AC coil, is fully saturated by the CD coil at a level, Bsat, such that it remains saturated in the condition of normal operation in static state CA. The saturable core FCL design shown in Figure 7 meets the four main criteria for an FCL and has the advantages of: 8 Minor mass through the absence of yokes and external columns. 0 Less footprint for a given loss current and steady state rate. ° Cost of economic construction. By reversing the relative locations of the AC and DC coils, the following technical benefits are also obtained: The structure becomes directly docile to high-voltage and extra-high voltage designs without requiring dielectric feed lines or vacuum to dielectric interfaces special The central part of the high permeability core can be submerged in a liquid or gaseous dielectric fluid with much of it so that an energy transformer is completely immersed in the dielectric fluid. Aspects of technology and the incorporation of knowledge about the design of high voltage transformers with synthetic silicone oil or other dielectrics, are applicable to this basic design including high voltage gaseous dielectrics such as SF6. This reduces the substantial risk involved in the design and development process for high voltage versions of these devices. Well-known standard materials used for immersion in liquid dielectrics and used at high static voltages can be used. The AC phase coils wrap an area of steel columns that is super saturated. The degree of electromagnetic influence of the AC coils is such that the insertion impedance is very close to the theoretical minimum that can be found. For example, as illustrated in Figure 9 and Figure 13. In these figures, the FEA has revealed that the relative permeability of the cores is very close to the unit despite the non-uniform distance from the coil CD of common magnetic field.

In another embodiment, the open cores are tapered toward the ends in a manner that keeps the entire core saturated. In the additional mode shown in Figure 15, the core poles of each phase are connected with a yoke, but remain open at one end. Figure 19 shows an FCL having a single open-phase core with the following details: • Core dimensions: 100 mm x 100 mm x 570 mm • Number of turns in each coil core CA: 20 • Number of turns in the CD polarization coil: 100 The results of the experimental arrangement shown in Figure 19 are provided in Figures 20 to 26. More particularly, Figure 20 shows the insertion impedance without steady state loss measured at 50 Hz through the terminals of the open-core FCL. There is a distinct change in the characteristic of the insertion impedance when sufficient DC bias is applied. In part A of Figure 20, below the minimum insertion impedance, the magnetic saturation of the high permeability core has not yet reached the full volume of the core under the magnetic influence of the AC coil. Hence, the measured insertion impedance is high. In part B of Figure 20, the saturation Magnetic core of high permeability has reached the degree of influence of the AC coil. This shows that a region of the high permeability core equal to at least the height of the AC coil must be saturated by the CD coil in order to obtain the minimum insertion impedance for the open core design. Figure 21 shows the characteristics of the steady-state lossless insertion impedance of the open-core FCL for a number of different voltage and current levels and shows that this amount is independent of the AC voltage level and the current level. The diagrams of the transient alternating current in Figure 22, display the difference in the loss current with and without the FCL placed in the measurement circuit. These data show that significant reductions in the loss current are possible for the open core FCL arrangement. Figure 23 shows the flux density measured in the steel core as a function of time during the loss current event. The loss current effectively desaturates the region of the steel core under the CA coils. This results in the FCL having a high impedance during the loss and, therefore, the intrinsic properties of loss current limitation.

The data shown in Figure 24 indicates that, if the high permeability core becomes sufficiently saturated, the transient voltage induced in the CD coil remains manageable and not unduly harmful during the loss. This is analogous to the classic design of the saturated FCL core. Figure 25 shows the transient loss current waveforms measured with the prospective loss current calculated after including the resistance of the AC coil and the inductive component without steady-state loss of the AC coil impedance of the FCL. The additional reduction in the loss current from a peak of 2,000 amperes to a peak of 1,100 amperes, is due to the additional change in magnetization after including the resistance of the AC coil and the insertion impedance without loss in steady state . Figure 26 shows the transit of the DC measured during the loss event to a number of different DC bias current values. The induced transient DC is negligible if the steel core is sufficiently polarized. Figure 27 shows an alternative experimental arrangement of the open-core FCL that includes yokes between the cores and that is designed to decrease the ampere turns of the CD polarization required for a low insertion impedance. The details of the designs are the following: • High permeability core dimensions: 100 mm x 100 mm x 570 mm (height) • Yoke dimensions: 100 mm x 100 mm x 250 mm (height) • Number of turns in each CA coil core: 20 • Number of turns of the CD polarization coil: 100 Figure 28 provides a comparison between the results of the insertion impedance obtained for the fixed and non-fixed configurations in which the insertion impedance characteristics are shown without loss in Stationary state measures 50 Hz of an open core FCL with and without yokes. Figure 29 shows that the fixation of the core arrangement inside the CD polarization coil changes the magnetization curve to the left, allowing to use fewer ampere turns to obtain a minimum insertion impedance. Figure 30 shows the total range of insertion impedance for the fixed configuration, which shows the significant improvement in the loss impedance of this arrangement at lower ampere turns applied DC. The loss-current diagrams for the experimental arrangement of the fixed open-core FCL in the Figure 31, show that the difference made by the presence of the fixed FCL for the various CD polarization modes compared to a system without FCL. The density of the magnetic flux in the highly permeable core material in the upper part of the CA coil was also measured in Figure 32 indicating the same characteristic behavior as in the fixed open core experimental arrangement. Figure 33 shows the waveforms of the transient current of the DC circuit through a range of different polarization levels. As for the non-fixed open-core FCL arrangement, the induced transient DC is negligible for sufficiently polarized cores. The main benefit of arranging the CD and AC coils, as illustrated in the embodiments, is that the AC coils experience the total CD density of the steel core under the CD coil. Classic designs of saturated FCL suffer from the disadvantage of transporting the flow from the CD columns to the CA columns through the upper and lower yokes and around the beveled joints within the core. The present modalities provide the yoke and the lateral columns CA making almost 100% efficient the transport of the flow from the CD coils to the CA. It will be appreciated that in the illustrated embodiments each leakage current limiter includes at least one input terminal in the form of an insulating bushing to be electrically connected to a power source, such as a transformer, which provides a load current. Each of the embodiments also includes at least one output terminal, also in the form of one or more high-voltage insulating bushes, for electrically connecting with a charging circuit, such as an electrical distribution system, which carries the charging current. . Also included is a magnetically saturable core and at least one AC coil, typically a coil for each phase of the load current, which is wound around a longitudinal portion of the core to carry the load current between the input terminal (s). and the terminal or output terminals. A CD coil induces a magnetic field in at least a portion of the core and extends around a longitudinal intermediate zone that receives the core and the coil. AC. In the illustrated modes, the intermediate zones are defined by respective tanks. The field induced by the CD coil magnetically polarizes the core in such a way that the AC coil moves from a low impedance state to a high impedance state in response to one or more characteristics of the load current. It will be appreciated that, in many applications, particularly when going to retro-aj to use an FCL to a existing facility, often the physical space available to accommodate the FCL is limited. Even more commonly, the most insignificant physical restriction is the footprint available for the FCL. Now, reference is made to Figures 35 and 36 where a single-phase open core FCL that has been developed for small footprint applications is illustrated. The FCL includes an input terminal in the form of a high-voltage insulating bushing for electrically connecting to a power source (not shown) that provides a charging current. An output terminal in the form of an additional high-voltage insulating bushing is electrically connected to a charging circuit (not shown) that carries the charging current. A magnetically saturable core has the shape of two similar high-permeability laminated steel posts extending longitudinally and stacked end-to-end with one another. An AC coil has two coil segments that are winding in opposite fashion on respective longitudinal portions of the poles for transporting the load current between the input terminal and the output terminal. A CD coil in the form of two separate sub-coils induces a magnetic field at least in the portions of the poles and extends around a longitudinal intermediate zone that receives the core and the coil CA. The zone, in this modality, is defined by the tank. The field magnetically polarises the poles in such a way that the AC coil moves from a low impedance state to a state of high impedance in response to one or more characteristics of the load current. An additional mode of small footprint is illustrated in Figures 37 and 38. In this embodiment, use is made of a depressed energy core. This provides a higher fill factor of the high permeability material within the cross-sectional area of the CA coil than could be achieved with laminations. Therefore, for the same footprint, and assuming that everything else is equal, the FCL of this modality provides improved performance over those of Figures 35 and 36. In a further embodiment, the FCL of Figures 37 and 38 is developed to provide the same performance as the FCL of Figures 35 and 36. Due to the higher fill factor, this additional mode has a smaller footprint than the FCL of Figures 37 and 38. Another embodiment of the FCL is illustrated in the Figures 39 and 40. This modality is a three-phase open-core FCL having three pairs of parallel and longitudinally coextensive posts, one pair of posts for each phase, to collectively define the core. The posts have a constant and uniform cross section that is asymmetrical. The pairs of posts include yokes, and the poles, the CA coils - - associated and yokes are all arranged within a tank containing a dielectric medium that also acts as a cooling medium. Figures 41 and 42 illustrate an additional embodiment that is similar to that of Figures 39 and 40, the main difference being the omission of the yokes to further reduce the amount of volume occupied by the FCL. It will be appreciated that the loss current limiters illustrated in Figures 39 to 42 include similar posts having asymmetric posts that are disposed relative to one another to generally define a cylinder. This configuration and the relative layout or relative orientation of the posts also contribute to a small footprint for the FCL. In other modalities, different procedures are taken to optimize the tread for. the FCL or, otherwise, to deal with any accommodation specification for a given site. For example, reference is made to Figure 43 which illustrates in FCL that it includes a core having rectangular poles in cross section disposed in a stacked arrangement of 3 x 2. The two coil segments for the AC coil of the same phase, are they find one arranged under the other. This open-core FCL configuration is used, for example, when the footprint of a site is limited and a greater height is allowed.

An additional embodiment is illustrated in Figure 44, wherein the FCL includes a core having rectangular poles in cross section disposed in a 3 x 2 side-by-side arrangement. This open-core FCL configuration is used, for example, when the height requirements are limited, but a greater footprint is allowed. A further example of an FCL including a core having rectangular poles in cross section disposed in a stacked 3 x 2 array that are fixed is illustrated in Figure 45. Compared with the "closed-core" saturable leakage current limiter type of paint frame, the above described modes have the following advantages: • A significant reduction required in the steel mass and therefore, a manufacturing cost, reduced transportation and site location • For similar performance, a reduction in footprint. This is particularly advantageous to lessen the problems of placement in dense urban locations. • In those cases in which a superconductor is used for the coil or CD polarization coils, a cryostat surface area less. This results in less loss of ambient heat in the steady state and, therefore, a lower requirement of freeze-cooling energy. • Mechanical decoupling of the CD polarization coil and the cryostat of the AC phase coils and the steel core. This allows the oil tank to descend into the hot drilling area of the CD coil, or the CD coils can descend onto the oil tanks containing the coils and phase cores. Compared with the alternative dispositions of the leakage current limiter such as resistive types, resistive types with external or internal reactor, protected core, solid state, the saturable open core loss current limiter has these advantages: Open core loss will not damage a protected line and does not need to be isolated from a protected line if any aspect of the superconducting portion fails, whether it is the CD coil, the vacuum system, or the cryogenic system. Therefore, the open-core loss current limiters of the modes are inherently safe in faults and are capable of being left on the protected line under these conditions. In addition, the redundancy associated with alarms and - - Internal fault detection has the ability to be less rigid compared to designs that must be disconnected from service for an internal fault. • None of the CD bias coils (either a superconducting coil or another) is directly connected to a high voltage or high current line in the network or power supply that is protected. Therefore, simple, established, and well known dielectric design procedures can be used to design the high voltage portion. • Liquid cryogens are not used as an AC dielectric and, therefore, there are no problems associated with these liquids in the design of the preferred modalities. • Superconducting elements are not charged by the loss current. Consequently, there is very little induction of current and voltage in the DC coil during a fault. • The superconductor is not hardened during a fault and, therefore, is capable of being used online when self-reclosing or reclosing logic is used in the switches and isolators of a protected line. The reference throughout this specification to - - "one (1) modality" or "one modality" means that a particular feature, structure or feature described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, the appearance of the phrases "in one (1) modality" or "in one modality" in various parts throughout this specification, they do not necessarily all refer to the same modality, but they could. In addition, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to that of ordinary experience in the art from this description, in one or more embodiments. Similarly, it should be appreciated that, in the foregoing description of the exemplary embodiments of the invention, various characteristics of the invention are grouped, sometimes, with one another in a single embodiment, Figure or description thereof, for the purpose of give channel to the description and help in the understanding of one or more of the various aspects of the invention. However, this method of description should not be interpreted as reflecting the claim that the claimed invention requires more features than those expressly cited in each claim. On the contrary, as reflected in the following claims, the aspects of the invention are based on less than all the characteristics of only one of the modalities described above. Therefore, the following claims are hereby expressly incorporated in the description of the invention, each claim supporting itself as a separate embodiment of this invention. Additional embodiments of the invention are described in Australian Patent Application No. 2009901138 filed on March 16, 2009 and of which priority is claimed. The detail of these modalities is expressly incorporated herein by way of cross reference. In addition, although some of the modalities described herein include some, but not others, characteristics included in other embodiments, the combinations of characteristics of different modalities, including the modalities described in the patent specifications of which the priority benefit is claimed. , they are intended to be within the scope of the invention and forms different modalities, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments may be used in any combination. In the description provided herein, numerous specific details are set forth. However, it understands that the embodiments of the invention can be practiced without these specific details. In other examples, well-known methods, structures and techniques have not been shown in detail so as not to obscure the understanding of this description. Those skilled in the art will recognize that these are examples applied to the specific designs that were manufactured and that detailed results will differ for other designs with different construction details. Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that it can be incorporated in many other ways.

Claims (25)

1. CLAIMS 1. A loss current limiter for incorporation into an electrical circuit, said loss current limiter including a magnetically saturable core and at least one AC phase coil wound around a portion of said saturable core, wherein said core magnetically saturable and said at least one phase coil CA are housed inside a housing and a CD polarization coil is arranged outside and around said housing which, during the operating conditions without loss of said current limiter, biases said Magnetic saturation core for a low insertion impedance, but during the loss conditions, extracts said core from the magnetic saturation to thereby provide an increased current limiting impedance in said electrical circuit.
2. 2. A leakage current limiter according to claim 1, which includes only one CD bias coil.
3. 3. A leakage current limiter according to claim 1, including two or more CD polarization coils.
4. 4. A leakage current limiter according to claim 3, wherein the CD bias coils are separated.
5. 5. A loss current limiter according to any one or more of claims 1 to 4, wherein said CD polarization coil is a high temperature superconductor.
6. 6. A loss current limiter according to claim 5, wherein said DC bias coil is coincident and coaxial with said at least one AC phase coil such that said portion of the saturable core is fully saturated. A loss current limiter according to claim 6, wherein said magnetically saturable core is in the form of an array of core posts with AC phase coils each wound on said respective electrically interconnected core posts of such that the senses of the magnetic fields produced by said CA coils are opposite. 8. A leakage current limiter according to claim 7, wherein said core posts are rectangular in cross section. 9. A leakage current limiter according to claim 7 or claim 8, wherein the core posts are connected by a yoke at one end and are open at the other end. 10. A leakage current limiter according to any of claims 7 to 9, wherein said core posts are of constant cross section along their lengths. 11. A leakage current limiter according to any of claims 7 to 10, wherein said core posts are tapered towards the ends thereof, whereby, during operation without loss of the limiter, substantially all said core is saturated. 12. A loss current limiter according to any of the preceding claims, wherein said limiter has an open core configuration. A loss current limiter according to claim 12, wherein a region of said core equal to at least the height of the AC coil is substantially and fully saturated by the CD coil in order to obtain the minimum impedance of insertion during the operating conditions without loss. A leakage current limiter according to any one of the preceding claims, wherein said magnetically saturable core is constructed of a rolling material of steel, mild steel or other magnetic steel, ferrite material, a high insulated compressed powder. permeability or a ferromagnetic material for transformer . 15. A leakage current limiter according to any of the preceding claims, wherein said magnetically saturable core and said AC phase coils are submerged in a dielectric. 16. A leakage current limiter according to claim 15, wherein said dielectric is in the form of a liquid or a gas. 1
7. 7. A loss current limiter according to claim 1 or claim 2, wherein said CD polarization coil is in the form of a common magnetic field CD coil. 1
8. 8. A leakage current limiter according to any of the preceding claims, wherein said housing includes a cooling means in addition to said dielectric. 1
9. 9. A leakage current limiter that includes: an input terminal to be electrically connected to a power source that provides a load current; an output terminal for electrically connecting with a charging circuit that carries the charge current; a magnetically saturable core; an AC coil wound around a longitudinal portion of the core to convey the load current between the input terminal and the output terminal; and a CD coil for inducing a magnetic field in at least a portion of the core and extending around an intermediate longitudinal zone that receives the core and the AC coil, where the field magnetically polarizes the core in such a way that the AC coil it moves from a state of low impedance to a state of high impedance in response to one or more characteristics of the load current. 20. A leakage current limiter according to claim 19, including two or more CD coils. 21. A leakage current limiter according to claim 20, wherein the CD coils are separated. 22. A leakage current limiter according to claim 19, wherein, in the low impedance state, the portion is magnetically saturated. 23. A leakage current limiter according to claim 22, wherein, in the low impedance state, the core is magnetically located saturated longitudinally beyond the portion. 24. A leakage current limiter according to any of claims 19 to 23, wherein, in the high impedance state, the portion is out of magnetic saturation. 25. A loss current limiter according to any of claims 19 to 24, wherein, in the low impedance state, the impedance of the AC coil is substantially equal to the theoretical impedance of the air core of the AC coil. .